Generally, a color gamut refers to a complete set of colors which can be produced by a system and serves to represent a range of colors which can be displayed by a certain apparatus. This concept is mainly specific to various types of display apparatuses, printers and printing apparatuses. Colors that can be represented by the nature and observed by human eyes constitute a largest color space. The larger the color space of a certain apparatus is, the more the colors that can be displayed by the apparatus will be, i.e., the stronger the capacity of displaying the colors in the nature will be.
In order to visually express the concept of “color gamut”, the International Commission on Illumination (CIE) prescribes a method for describing the color gamut by utilizing a CIE-xy chromaticity diagram. In the CIE-xy chromaticity diagram as illustrated in FIG. 5, the horseshoe-shaped graph represents all color types yin the nature, and the triangle-shaped graphs constituted by lines connecting blue point, green point and red point represent respective ranges of color gamut which can be displayed by various types of apparatuses; wherein the triangle-shaped graph with a larger area indicates a wider range of color gamut which can be displayed by the corresponding apparatus. At present, colors are basically displayed by using RGB as the three-primary colors; however, even under the circumstance that the lasers of RGB three colors are employed, the triangle-shaped regions of color gamut still cannot cover all the colors sensed by the human eyes. Well-known imaging devices have difficulty in fully representing all the colors in the nature due to a narrow color gamut of a light source assembly which provides the imaging device with light beams.